Last week, the World Health Organization reported that an estimated 8.2 million deaths a year are linked to air pollution.
And that number is on the rise.
The most harmful pollutant to human health is called PM 2.5, short for particle matter that's less than 2.5 microns in diameter. It's found in soot, smoke, and dust and lodges in the lungs causing long-term health problems like asthma and chronic lung disease.
PM 2.5 starts to become a health problem when there is more than 35.5 micrograms of PM 2.5 per cubic meter (written like 35.5 µg/m3) of air, according to the Environmental Protection Agency. But WHO recommends that PM 2.5 shouldn't even exceed 10 µg/m3.
The most polluted cities on Earth have anywhere from nine to 15 times that amount — based on information from the WHO — and you might be surprised which make the top 10 list. Check them out:
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10. Lucknow, India - 96 µg/m3 of PM 2.5
Lucknow, a city in northern India, starts off the top 10 cities with the worst air pollution levels list. It still significantly has a high average air pollution level that falls into the "unhealthy" category. Vehicle emissions are a major factor in Lucknow's air pollution problem.
9. Ahmedabad, India - 100 µg/m3 of PM 2.5
India's western city Ahmedabad gets its air pollution in part from the major construction happening in the city.
8. Khorramabad, Iran - 102 µg/m3 of PM 2.5
Khorramabad, a city in western Iran, had the country's highest air pollution levels. One of the most populous cities in Iran, Khorramabad is an agriculture hub, which likely contributes to its air pollution problems.
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